1. Field of the Invention
This invention relates to a full-color hard copy imaging system and an imaging process, to achieve a full color image.
2. Description of Related Art
Many ways of creation of a full-color hard copy image by thermal transfer of dyes on to a receiver sheet are well known. One system described in U.S. Pat. No. 4,833,124; 4,927,803; and U.S. Pat. No. 4,775,657 obtains prints from pictures which have been generated electronically from a color video camera. According to one way of obtaining such prints, an electronic picture is first subjected to color separation by color filters. The respective color-separate images are then converted into electrical signals. These signals are then operated on to produce cyan, magenta and yellow electrical signals. These signals are then transmitted to a thermal printer. To obtain the print, a cyan magenta or yellow dye-donor element is placed face-to-face with a dye-receiving element. The two are then inserted between a thermal printing head and a platen roller. A line-type thermal printing head is used to apply heat from the back of the dye-donor sheet. The thermal printing head has many heating elements and is heated up sequentially in response to the cyan, magenta and yellow signals. The process is then repeated for the other two colors. A color hard copy is thus obtained which corresponds to the original picture viewed on a screen. Further details of this process and an apparatus for carrying it out are contained in U.S. Pat. No. 4,621,271 by Brownstein entitled "Apparatus and Method For Controlling A Thermal Printer Apparatus", issued Nov. 4, 1986.
A second system described in U.S. Pat. No. 4,587,198 sets forth a process for providing a colored image comprising exposing a radiation sensitive layer over a vapor deposited colorant layer and vaporizing the colorant to selectively transmit the colorant through the exposed layer. The change in solubility, penetrability and/or crosslinking polymerization causes differential migration through the exposed layer.
Japanese Kokai 69-55429; 1982 discloses a method of forming color images by thermal development, by processing a silver salt light sensitive material containing dye by thermal development, thereby conducting tanning developing, imagewise hardening a silver salt light sensitive material binder, suppressing diffusion of said dyes from the binder to an image receiving layer and imagewise forming color images to the image receiving layer.
A full-color hard copy imaging system is shown in U.S. Pat. No. 4,576,891 in which the donor sheet is coated with three types of microencapules. The first type of microencapules comprise a cyan dye-former and a photocrosslinkable composition that crosslinks upon exposure to red light, the second type of microencapsules comprise a magenta dye-former and a photocrosslinkable composition that crosslinks upon exposure to green light and a third type of microencapsules comprise a yellow dye-former and a photocrosslinkable composition that crosslinks upon exposure to blue light. The donor sheet is exposed with a multicolor positive image and then laminated to a receiver sheet through a hot pressure roller. The receiver sheet is coated with a layer containing a universal development agent for the three dye formers. Under pressure and heat the uncrosslinked capsules rupture and the dye-formers of all the three colors are transferred to this receiver sheet, when they imagewise form three color dyes producing a full-color image. The major advantage of this system is that a full-three color image is formed in a single lamination and pressure development step However, the disadvantages associated with the process is that the microencapsules are in a range of diameters between 1 to 25 microns. Therefore, the resolution of the system is limited to size of the largest microencapsules.